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United States Patent |
6,018,198
|
Tsuzuki
,   et al.
|
January 25, 2000
|
Hybrid drive apparatus for vehicle
Abstract
A hybrid drive apparatus for a vehicle which is capable of improving the
response in restarting an engine during the running of a vehicle. As a
result, a shock due to deceleration can be reduced. The hybrid drive
apparatus for a vehicle incorporates an engine, a motor generator, a
clutch, a transmission unit and a control unit for controlling the other
elements. The control unit incorporates a standby control device for
realizing a constant cranking characteristic to improve the starting
response at the start of the engine by transmitting the power of the motor
generator to the engine and controlling the engagement pressure of the
clutch, thus revolving the engine to a cranking start position.
Inventors:
|
Tsuzuki; Shigeo (Anjo, JP);
Kurita; Kiyoshi (Anjo, JP);
Matsushita; Yoshinori (Anjo, JP)
|
Assignee:
|
Aisin AW Co., Ltd. (Anjo, JP)
|
Appl. No.:
|
135643 |
Filed:
|
August 18, 1998 |
Foreign Application Priority Data
Current U.S. Class: |
290/17; 180/65.2; 290/40C; 322/16 |
Intern'l Class: |
F02N 011/00 |
Field of Search: |
290/17,40 R,40 B,40 C
322/16
180/165,65.2
123/331
|
References Cited
U.S. Patent Documents
5343970 | Sep., 1994 | Saverinsky | 180/65.
|
5713814 | Feb., 1998 | Hara et al. | 477/5.
|
5720690 | Feb., 1998 | Hara et al. | 477/20.
|
5735770 | Apr., 1998 | Omote et al. | 477/5.
|
5801499 | Sep., 1998 | Tsuzuki et al. | 318/141.
|
5818116 | Oct., 1998 | Nakae et al. | 290/38.
|
5839533 | Nov., 1998 | Mikami et al. | 180/165.
|
5846155 | Dec., 1998 | Taniguchi et al. | 477/2.
|
5856709 | Jan., 1999 | Ibaraki et al. | 290/45.
|
5951614 | Sep., 1999 | Tabata et al. | 701/54.
|
Primary Examiner: Ponomarenko; Nicholas
Attorney, Agent or Firm: Oliff & Berridge, PLC
Claims
What is claimed is:
1. A hybrid drive apparatus for a vehicle, comprising
an engine;
a motor generator;
a transmission unit capable of transmitting the power of said engine and
said motor generator to wheels; and
a control unit for controlling said engine, said motor generator and
transmission of power of said engine and said motor generator to the
wheels, wherein said control unit incorporates:
starting control means for starting said engine when a vehicle is driven in
a state where said engine is stopped and power of said motor generator is
transmitted to the wheels, and
standby control means for performing control to revolve said engine to a
cranking start position prior to the start of said engine performed by
said starting control means.
2. The hybrid drive apparatus according to claim 1, further comprising a
clutch between said engine and said motor generator, wherein
said standby control means incorporates standby pressure control means for
controlling a clutch pressure such that the capacity of torque transmitted
by said clutch becomes a capacity that allows said engine to revolve to
the cranking start position.
3. The hybrid drive apparatus according to claim 2, wherein said starting
control means incorporates cranking pressure control means for controlling
the engagement pressure of said clutch such that the capacity of torque
transmitted by said clutch becomes less than or equal to an output torque
from said motor generator subsequent to the standby control.
4. The hybrid drive apparatus according to claim 2, further comprising a
starter motor for starting said engine, wherein said starting control
means directs said starter motor to start and said clutch to be brought to
engagement simultaneously after completion of the standby control.
5. A hybrid drive apparatus for a vehicle, comprising:
an engine;
a motor generator;
a clutch capable of controlling power transmission between said engine and
said motor generator;
a transmission unit capable of transmitting the power of said engine and
said motor generator to wheels; and
a control unit for controlling said engine, said motor generator and said
clutch, wherein said control unit incorporates:
starting control means for engaging said clutch so as to start said engine
when a vehicle is driven in a state where said engine is stopped, said
clutch is disengaged to allow said motor generator to transmit its power
to the wheels; and
standby control means for performing control to bring said clutch to
engagement to revolve said engine to a cranking start position prior to
the start of said engine performed by said starting control means, said
standby control means incorporating standby pressure control means for
controlling the engagement pressure of said clutch such that the capacity
of torque transmitted by said clutch becomes a capacity that allows said
engine to revolve to the cranking start position, and said starting
control means incorporating cranking pressure control means for
controlling the engagement pressure of said clutch such that the capacity
of torque transmitted by said clutch becomes equal to or lower than an
output torque from said motor generator subsequent to the standby control.
6. A hybrid drive apparatus for a vehicle, comprising:
an engine;
a motor generator;
a starter motor for starting said engine;
a clutch capable of controlling power transmission between said engine and
said motor generator;
a transmission unit capable of transmitting the power of said engine and
said motor generator to wheels; and
a control unit for controlling said engine, said motor generator, said
starter motor and said clutch, wherein said control unit incorporates:
starting control means for starting said engine when a vehicle is driven in
a state where said engine is stopped, said clutch is disengaged and the
power of said motor generator is transmitted to the wheels, and
standby control means for performing control to bring said clutch to
engagement to revolve said engine to a cranking start position prior to
the start of said engine performed by said starting control means, said
standby control means incorporating standby pressure control means for
controlling the engagement pressure of said clutch such that the capacity
of torque transmitted by said clutch becomes a capacity that allows said
engine to revolve to the cranking start position, and said starting
control means starting said starter motor and bringing said clutch to
engagement simultaneously with completion of the standby control.
7. The hybrid drive apparatus according to claim 5, wherein said cranking
pressure control means incorporates constant acceleration control means
for controlling the engagement pressure of said clutch such that a rate of
change in the revolutions of said engine is set to a required value.
8. The hybrid drive apparatus according to claim 5, wherein said cranking
pressure control means incorporates revolution maintaining and controlling
means for controlling the engagement pressure of said clutch such that the
rate of decrease in the revolutions of said motor generator becomes less
than or equal to a predetermined value.
9. The hybrid drive apparatus according to claim 6, wherein said starting
control means incorporates start-up control means for operating said
starter motor only for a period of time in which said engine is slightly
revolving.
10. The hybrid drive apparatus according to claim 6, wherein said starting
control means incorporates cranking pressure setting means for setting the
engagement pressure of said clutch to a value with which said clutch
transmits an average value of cranking torque of said engine.
11. The hybrid drive apparatus according to claim 6, wherein said starting
control means incorporates torque control means for causing said motor
generator to produce an output of the average value of the cranking torque
of said engine and an output of the torque for driving the vehicle.
12. The hybrid drive apparatus according to claim 6, wherein said starting
control means incorporates torque control means for causing said motor
generator to produce an output of the torque corresponding to a starting
current for said starter motor.
13. The hybrid drive apparatus according to claim 6, wherein a time for
operating said starter motor is controlled by a timer.
14. The hybrid drive apparatus according to claim 5, wherein said starting
control means incorporates torque control means for causing said motor
generator to output maximum torque and pressure increase means for
increasing the engagement pressure to increase the torque capacity of said
clutch when said motor generator produces an output of maximum torque.
15. The hybrid drive apparatus according to claim 5, wherein said starting
control means incorporates torque control means for causing said motor
generator to output an average value of cranking torque of said engine.
16. The hybrid drive apparatus according to claim 5, wherein said starting
control means incorporates sweep-up means for sweeping up the engagement
pressure of said clutch.
17. The hybrid drive apparatus according to claim 5, wherein said standby
control means incorporates fast-fill-pressure supply means for shortening
a piston stroke of said clutch.
18. The hybrid drive apparatus according to claim 5, wherein said control
unit has a clutch standby region set between a motor drive region and an
engine drive region.
19. The hybrid drive apparatus according to claim 5, wherein said starting
control means supplies fuel to said engine for ignition when the
revolutions of said engine have reached a predetermined number of
revolutions per unit time.
20. The hybrid drive apparatus according to claim 5, wherein said starting
control means brings said clutch to complete engagement subsequent to
synchronization of revolutions of said engine and said motor generator.
21. The hybrid drive apparatus according to claim 5, wherein said control
unit incorporates completion control means for sweeping down the output
torque from said motor generator and enlarging a throttle opening of said
engine.
22. The hybrid drive apparatus according to claim 6, wherein said standby
control means incorporates fast-fill-pressure supply means for shortening
the piston stroke of said clutch.
23. The hybrid drive apparatus according to claim 6, wherein said control
unit has a clutch standby region set between a motor drive region and an
engine drive region.
24. The hybrid drive apparatus according to claim 6, wherein said starting
control means supplies fuel for ignition when the revolutions of said
engine have reached a predetermined number of revolutions per unit time.
25. The hybrid drive apparatus according to claim 6, wherein said starting
control means brings said clutch to complete engagement subsequent to
synchronization of revolutions of said engine and said motor generator.
26. The hybrid drive apparatus according to claim 6, wherein said control
unit incorporates completion control means for sweeping down the output
torque from said motor generator and enlarging a throttle opening of said
engine.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a hybrid drive apparatus for a vehicle
incorporating an engine and a motor generator as power sources thereof,
and more particularly, to an art for restarting an engine that has been
stopped in a state where the vehicle is driven by a motor generator for
reducing fuel consumption.
2. Description of the Related Art
A hybrid drive apparatus is known as a drive apparatus for a vehicle which
incorporates a combustion engine (hereinafter called an "engine") and an
electric motor generator (hereinafter called a "motor generator") each
serving as a power source. The engine, one of the power sources, is
characterized in that the decrease rate of efficiency is rapidly raised to
match the decrease rate in the load in a lighter load region.
In order to reduce fuel consumption for energy saving, a drive apparatus
has been disclosed which is adapted to a method of automatically stopping
an engine and driving the vehicle by a motor generator at a light load,
that is, the state where the amount of depression of an accelerator
(hereinafter called an "accelerator opening") assumes a small value. In
the above-mentioned method, the engine has to be automatically restarted
when the accelerator opening is set to be more than the small value. At
this time, while a portion of the driving force of the motor generator is
used for running the vehicle, another portion is used to start the engine.
Therefore, there is a decrease in the driving force due to the cranking
load for the engine which gives the driver of the vehicle a feeling of
excessive deceleration. Thus, a method is required to overcome the
aforementioned problem by reducing the shock resulting from deceleration
at the time of restarting the engine.
As a measure for preventing shock owing to deceleration, a technology is
known to sweep up the engagement pressure of the clutch between the motor
generator and the engine and to recognize a changing rate in the slight
revolution of the motor generator caused by the increase in transmission
force of the torque in the clutch engagement. Then, the output torque of
the motor generator rises.
The cranking load generated when restarting the engine becomes a synthetic
torque combining the torque of resistance generated by intake, compression
and exhaust strokes in each cylinder, the torque corresponding to
mechanical dragging resistance, and the torque for operating auxiliary
units, such as an air conditioner, an alternator, a water pump and an oil
pump with the inertia torque required to accelerate the stopped engine.
Above all, the load generated by the intake/exhaust operations becomes a
periodically oscillating torque as indicated by lines having different
symbols respectively corresponding to the cylinders shown in FIG. 12. The
total value of the aforementioned torque has a characteristic indicated by
a solid line.
The actual cranking torque is characterized in that it is sharply increased
to assume an excessive high torque value only at the start of revolution
and then it assumes a substantially constant value as shown in FIG. 13.
This is because inertia torque as a resistance against the revolutions, in
turn, is caused to restrain the oscillation of the torque by flywheel
inertia after the engine has been started. Therefore, the cranking torque
which is needed in order to maintain revolutions at a predetermined speed
may assume an average value.
Accordingly, a technology has been suggested to prevent generation of any
load during intake/exhaust operations until the engine has been restarted
to reach a certain number of revolutions in accordance with the
characteristic of the cranking torque. Thus, the peak value of the torque
load is reduced so as to decrease the cranking torque applied to the motor
generator.
However, the latter technology requires reorganization of the engine as
well as complicated control. Therefore, many problems have to be solved
for a practical application. Meanwhile the former technology has a problem
caused by the characteristic of the cranking torque. That is, the start-up
characteristic of the cranking torque having the aforementioned
periodically oscillating torque component is changed because the position
of the peak is shifted from the crank shaft position at a stop state of
the engine, as shown by a chain line, to that shown by the solid line of
FIG. 14. As the timing of the generation of the peak torque is shifted as
described above, the hydraulic pressure for engaging the clutch has to be
changed to correspond to the foregoing capacity. Therefore, very precise
control must be performed such that the amount of the increase in output
torque from the motor generator is changed to correspond to the foregoing
hydraulic pressure. This precise control cannot be performed by a simple
control, such as a control using a map. Because the control cannot
accurately estimate the oscillating torque component generated by the
compression and expansion strokes in the cylinder, a shock is easily
caused in an initial stage of starting the engine. What is worse, a
satisfactorily high control speed cannot be realized.
SUMMARY OF THE INVENTION
Accordingly, a first object of the invention is to provide a hybrid drive
apparatus for a vehicle which is capable of making a cranking
characteristic at the restart of the engine constant so that the engine is
restarted with a good response under a simple control in a state where the
vehicle is driven by the motor generator.
A second object of the invention is to realize a standby state by hydraulic
control for making the cranking characteristic constant.
A third object of the invention is to enable the standby state for making
the cranking characteristic constant and to realize the subsequent
starting in a limited range of output from the motor generator.
In order to prevent a shock owing to the decrease in the driving force at
the restart of the engine, a motor generator having a large capacity for
outputting a sufficiently great torque must be employed. Moreover, control
for increasing the output torque in accordance with the cranking load must
be performed. If the motor generator having the large capacity is mounted
only to start the engine, the size of the motor generator becomes
unnecessarily enlarged. The capacity of an inverter for controlling the
motor generator is accordingly increased, leading to the increased
capacity of the battery. Thus, the above-mentioned method cannot
effectively solve the problems.
Accordingly, a fourth object of the invention is to provide a hybrid drive
apparatus for a vehicle which employs a starter motor provided for an
engine so as to supplementarily be operated to crank the engine at a
satisfactory response without enlarging the motor generator for performing
cranking under simple control of the engagement pressure of the clutch.
A fifth object of the invention is to provide a hybrid drive apparatus for
a vehicle which is capable of realizing a standby state for making the
cranking characteristic constant and subsequent start by a motor generator
without using a special auxiliary drive means.
A general method is known, which starts an engine by a starter motor. If
the above-mentioned method is simply applied to restart the engine during
running of the vehicle, a disturbing noise is generated due to variance in
the cranking torque and the starting response cannot satisfy the
requirement. Accordingly, a sixth object of the invention is to provide a
hybrid drive apparatus for a vehicle which employs a starter motor
provided for an engine so as to supplementarily be operated at start-up of
the engine revolution requiring substantially high torque at cranking and
to enable engine cranking at a good response without enlarging the motor
generator for cranking under a simple control of the engagement pressure
of the clutch.
When the engine is started only by the motor generator, various methods may
be employed to control the engagement pressure of the clutch to increase
the number of revolutions of the engine for cranking the engine. If the
control of the engagement pressure becomes complicated, a method of the
foregoing type cannot practically be employed. Accordingly, a seventh
object of the invention is to restart an engine by simply controlling the
engagement pressure of the clutch.
When starting the engine only by the motor generator, generation of a
deceleration shock owing to cranking of the engine cannot be prevented
under the limited output of the motor generator. When the deceleration
feeling is limited to fall in a predetermined range, a sensible shock can
be prevented. Accordingly, an eighth object of the invention is to restart
the engine while preventing reduction in the number of revolutions of a
motor generator to satisfy a predetermined range under control of the
engagement pressure of a clutch.
As a starter motor provided for the engine is not operated frequently, it
is operated in an overload state requiring substantially high electric
current. However, when using the starter motor frequently for restarting
the engine in the same overload state, there might be deterioration in
durability of the starter motor. Accordingly, a ninth object of the
invention is to maintain durability of the starter motor by operating the
starter motor in a light load state where the cranking torque is
compensated by a motor generator such that the operation time is greatly
limited.
As described above, the cranking torque for starting the engine becomes
high while starting the revolution of the engine and the subsequent torque
is decreased. Accordingly, a tenth object of the invention is to simplify
the control of the engagement pressure of the clutch for torque
transmission by supplementarily operating a starter motor to average the
increased output torque of the motor generator all through the engine
start-up period.
When the starter motor is supplementarily operated during the revolution
start-up period, the increase in the output torque from the motor
generator can be decreased all through the engine start period.
Accordingly, an eleventh object of the invention is to decrease the torque
load of the motor generator for starting the engine and simplifying the
output torque control.
As a method for preventing the torque of the motor generator from being
used for starting the engine, it might be feasible to employ a method for
restarting the engine during running only by the starter motor. If the
foregoing method is employed, durability of the starter motor may be
deteriorated for the aforementioned reason. Accordingly, a twelfth object
of the invention is to maintain the durability of the starter motor even
if the starter motor is mainly used and the torque of the motor generator
is supplementarily used to restart the engine during running.
A thirteenth object of the invention is to simplify the control of the
starter motor under the start-up control.
A fourteenth object of the invention is to restart the engine with good
response only by the motor generator torque while suppressing the
generation of deceleration shock to a minimum.
A fifteenth object of the invention is to simplify the torque-control of
the motor generator torque under starting control in accordance with
control of the engagement pressure of the clutch.
A sixteenth object of the invention is to perform the torque-control of the
motor generator torque when the standby control is shifted to the starting
control using a very simple method.
A seventeenth object of the invention is to improve response of a standby
control prior to the starting control by the motor generator.
The drive mode in the conventional hybrid drive apparatus is switched such
that a reference is made to a drive mode map stored in a microcomputer of
a control unit and having drive regions determined in accordance with the
relationship between the degree of accelerator opening and vehicle speed.
Moreover, the foregoing switching operation is performed in accordance
with the relationship between the degree of accelerator opening at each
moment in time and the vehicle speed. An eighteenth object of the
invention is to restart the engine by performing a simple control using a
map in which the time for starting the standby control has been set.
It is important to confirm start of the engine in order to complete the
engine starting control in a period of time as short as possible.
Accordingly, a nineteenth object of the invention is to accurately
determine the start of the engine.
A twentieth object of the invention is to smoothly finish the engine
starting control with the motor generator.
A twenty-first object of the invention is to smoothly shift the motor drive
to the engine drive after the engine has been started.
A twenty-second object of the invention is to improve the response of a
standby control performed prior to the starting control with the starter
motor.
A twenty-third object of the invention is to restart the engine by
performing a simple control using a map on which the starting time of the
standby control has been set prior to the starting control using the
starter motor.
A twenty-fourth object of the invention is to cause the engine to
spontaneously revolve at a good timing in a final stage of the starting
control by appropriately resuming the fuel supply and performing ignition.
A twenty-fifth object of the invention is to smoothly terminate the engine
starting control using a starter motor.
A twenty-sixth object of the invention is to smoothly shift motor drive to
engine drive subsequent to the start of the engine under the engine
starting control using a starter motor.
To achieve the first object, according to one aspect of the invention,
there is provided a hybrid drive apparatus for a vehicle, provided with an
engine, a motor generator, a transmission unit capable of transmitting the
power of the engine and the motor generator to the wheels, and a control
unit for controlling the engine, the motor generator and the transmission
of power of the engine and the motor generator to the wheels. The control
unit incorporates starting control means for starting the engine when a
vehicle is driven in a state where the engine is stopped and power of the
motor generator is transmitted to the wheels, and standby control means
for performing control to revolve the engine to a cranking start position
prior to the start of the engine performed by the starting control means.
To achieve the second object, a hybrid drive apparatus for a vehicle
further includes a clutch capable of controlling power transmission
between the engine and the motor generator. The standby control means
incorporates standby pressure control means for controlling a clutch
pressure such that the capacity of the torque transmitted by the clutch
becomes a capacity that allows the engine to revolve to the cranking start
position.
To achieve the third object, the starting control means incorporates
cranking pressure control means for controlling the engagement pressure of
the clutch such that the capacity of the torque transmitted by the clutch
becomes less than or equal to an output torque from the motor generator
subsequent to the standby control.
To achieve the fourth object, the hybrid drive apparatus for a vehicle
further includes a starter motor for starting the engine. The starting
control means causes the starter motor to start and the clutch to be
brought to engagement simultaneously subsequent to the standby control.
To achieve the fifth object, there is provided a hybrid drive apparatus for
a vehicle including an engine, a motor generator, a clutch capable of
controlling power transmission between the engine and the motor generator;
a transmission unit capable of transmitting the power of the engine and
the motor generator to the wheels; and a control unit for controlling the
engine, the motor generator and the clutch. The starting control means for
engaging the clutch so as to start the engine when a vehicle is driven in
a state where the engine is stopped, the clutch is disengaged to allow the
motor generator to transmit its power to the wheels, and standby control
means for performing control to bring the clutch to engagement to revolve
the engine to a cranking start position prior to the start of the engine
performed by the starting control means. The standby control means
incorporates standby pressure control means for controlling the engagement
pressure of the clutch such that the capacity of the torque transmitted by
the clutch becomes a capacity that allows the engine to revolve to the
cranking start position. The starting control means incorporates cranking
pressure control means for controlling the engagement pressure of the
clutch such that the capacity of the torque transmitted by the clutch
becomes equal to or lower than an output torque from the motor generator
subsequent to the standby control.
To achieve the sixth object, there is provided a hybrid drive apparatus for
a vehicle including an engine, a motor generator, a starter motor for
starting the engine, a clutch capable of controlling power transmission
between the engine and the motor generator, a transmission unit capable of
transmitting the power of the engine and the motor generator to wheels,
and a control unit for controlling the engine, the motor generator, the
starter motor and the clutch. The control unit incorporates starting
control means for starting the engine when a vehicle is driven in a state
where the engine is stopped, the clutch is disengaged and the power of the
motor generator is transmitted to the wheels, and standby control means
for performing control to bring the clutch to engagement to revolve the
engine to a cranking start position prior to the start of the engine
performed by the starting control means. The standby control means
incorporates standby pressure control means for controlling the engagement
pressure of the clutch such that the capacity of the torque transmitted by
the clutch becomes a capacity that allows the engine to revolve to the
cranking start position, and the starting control means starts the starter
motor and brings the clutch to engagement simultaneously subsequent to the
standby control.
To achieve the seventh object, the cranking pressure control means
incorporates constant acceleration control means for controlling the
engagement pressure of the clutch such that a rate of change in the
revolutions of the engine is set to a required value.
To achieve the eighth object, the cranking pressure control means
incorporates revolution maintaining and controlling means for controlling
the engagement pressure of the clutch such that the rate of decrease in
the revolutions of the motor generator becomes equal to or lower than a
predetermined value.
To achieve the ninth object, the starting control means incorporates
start-up control means for operating the starter motor only for a period
of time in which the engine is slightly revolving.
To achieve the tenth object, the starting control means incorporates
cranking pressure setting means for setting the engagement pressure of the
clutch to a value with which the clutch transmits an average value of the
cranking torque of the engine.
To achieve the eleventh object, the starting control means incorporates
torque control means for causing the motor generator to produce an output
of the average value of the cranking torque of the engine and an output of
the torque for driving the vehicle.
To achieve the twelfth object, the starting control means incorporates
torque control means for causing the motor generator to produce an output
of the torque corresponding to a starting current for the starter motor.
To achieve the thirteenth object, a time for operating the starter motor is
controlled by a timer.
To achieve the fourteenth object, the starting control means incorporates
torque control means for causing the motor generator to output maximum
torque and pressure increase means for increasing the engagement pressure
to increase the torque capacity of the clutch when the motor generator
produces an output of maximum torque.
To achieve the fifteenth object, the starting control means incorporates
torque control means for causing the motor generator to output an average
value of cranking torque of the engine.
To achieve the sixteenth object, the starting control means incorporates
sweep-up means for sweeping up the engagement pressure of the clutch.
To achieve the seventeenth object, the standby control means incorporates
fast-fill-pressure supply means for shortening a piston stroke of the
clutch.
To achieve the eighteenth object, the control unit has a clutch standby
region set between a motor drive region and an engine drive region.
To achieve the nineteenth object, the starting control means supplies fuel
to the engine for ignition when the revolutions of the engine have reached
a predetermined revolution.
To achieve the twentieth object, the starting control means brings the
clutch to complete engagement subsequent to synchronization of revolutions
of the engine and the motor generator.
To achieve the twenty-first object, the control unit incorporates
completion control means for sweeping down the output torque from the
motor generator and enlarging a throttle opening of the engine.
To achieve the twenty-second object, the standby control means incorporates
fast-fill-pressure supply means for shortening the piston stroke of the
clutch.
To achieve the twenty-third object, the control unit has a clutch standby
region set between a motor drive region and an engine drive region.
To achieve the twenty-fourth object, the starting control means supplies
fuel for ignition when the revolutions of the engine have reached a
predetermined number of revolutions.
To achieve the twenty-fifth object, the starting control means brings the
clutch to complete engagement subsequent to synchronization of the
revolutions of the engine and the motor generator.
To achieve the twenty-sixth object, the control unit incorporates
completion control means for sweeping down the output torque from the
motor generator and for enlarging a throttle opening of the engine.
According to the invention, the hybrid drive apparatus for a vehicle is
structured such that cranking of the engine is always started in a state
where the engine is controlled to revolve to the cranking start position
by the standby control means. Unlike the cranking performed at an
indefinite position, the above-identified cranking can easily be
controlled. Thus, the engine can stably be started within a predetermined
period of substantially a short time. Therefore, the above-mentioned
structure allows restart of the engine with satisfactory response while
being driven by the motor generator. As a result, a great decrease in the
driving torque generated at the restart of the engine can be prevented
under the simple starting control.
Because the standby control is performed such that the engagement pressure
of the clutch is controlled by the standby pressure control means to limit
the torque capacity, the engine can reliably be revolved to the cranking
start position using the motor generator torque.
Because the engine is cranked such that the engagement pressure of the
clutch is controlled by the cranking pressure control means to limit the
capacity of transmitted torque to a value equal to or smaller than the
output torque of the motor generator, the engine can be cranked within the
torque which can be produced.
As the starter motor is started by the starting control means
simultaneously with the engagement of the clutch, the torque of the
starter motor can effectively be used when a large torque is required at
the start-up of the engine revolution in an initial stage of the cranking
process.
At a standby state where the cranking characteristic is kept constant,
cranking of the engine enables a start with the torque less than or equal
to the output torque of the motor generator. Therefore, the motor
generator is allowed to realize the standby state for cranking the engine
and to start subsequent to the cranking operation without any particular
auxiliary drive means.
When performing the start of the engine requiring great torque after the
standby state for making the cranking characteristic constant has been
realized, the starter motor provided for the engine is supplementarily
used. Thus, the engine can be cranked while decreasing both of the load of
the motor generator and that of the starter motor. Therefore, the
aforementioned structure is able to restart the engine with satisfactory
response without enlarging the motor generator for cranking.
Because the engagement pressure of the clutch is controlled such that the
rate of change in the revolutions of the engine is kept constant in
cranking the engine, the engine can be restarted by simply controlling the
engagement pressure of the clutch.
The engagement pressure of the clutch is controlled such that a decrease in
the number of revolutions of the motor generator falls within a
predetermined range in cranking the engine. Therefore, starting control
can be performed in accordance with a deceleration feeling based on the
number of revolutions of the motor generator.
Because starting control is performed such that the starter motor is
operated at a light load to compensate for the cranking torque generated
by the motor generator for a limited period, durability of the starter
motor is maintained while reducing both the load of the motor generator
and the load of the starter motor at cranking.
As the starter motor is supplementarily used when revolution is started in
an initial stage of cranking and the output torque from the motor
generator is increased to assume an average value during the engine start
period, control of the engagement pressure of the clutch for transmitting
the torque can be simplified.
When revolution is started, the starter motor is supplementarily used and
the output torque from the motor generator is increased to assume an
average value during the engine start period, control of the output torque
can be simplified while reducing the torque load of the motor generator
for starting the engine.
The engine is started such that the starter motor is mainly used and the
motor generator torque is supplementarily used. Therefore, control can be
performed such that torque for cranking the motor generator is decreased,
thus minimizing the influence on the driving torque. Moreover, durability
of the starter motor is maintained.
The starter motor during starting control is simplified.
As the engine is cranked at a maximum torque which can be produced by the
motor generator, the engine can be restarted with a satisfactory response
only by the motor generator while preventing generation of a deceleration
shock.
Because the engine can be cranked at a predetermined acceleration while
causing the motor generator to produce an output of predetermined torque
at the starting control, the control of the motor generator can be
simplified.
According to the invention, the control of the engagement pressure of the
clutch performed at a transition from the standby control to the starting
control can be simplified.
Because the starting control by the motor generator can be performed so as
to quickly complete the piston stroke of the clutch for the purpose of
performing the standby control, the response of the standby control is
improved.
As the start timing of the standby control can easily be determined in
accordance with a determination of the region, the logic for the standby
control can be simplified and the standby control can quickly be executed.
Because fuel is supplied to the engine for ignition at a timing when the
number of revolutions of the engine has reached a predetermined value, the
engine can appropriately be started.
According to the invention, the engine starting control by the motor
generator can smoothly be completed.
According to the invention, transition from the motor drive to the engine
drive can smoothly be performed subsequent to the start of the engine.
According to the invention, the starting control using the starter motor
can be performed such that the piston stroke of the clutch for the standby
control can quickly be executed, thus improving response of the standby
control.
As the start timing of the standby control can easily be determined by
determining the region at restarting by the starter motor, the standby
control can quickly be executed while simplifying the logic thereof.
Because control is performed such that the fuel supply and ignition is
performed at a timing when the number of revolutions thereof has reached a
predetermined value at restarting using the starter motor, the engine can
appropriately be started.
According to the invention, the engine starting control using the motor
generator and the starter motor can smoothly be executed.
According to the invention, transition from the motor drive to the engine
drive subsequent to the engine start by the motor generator and the
starter motor can smoothly be executed, respectively.
Other objects, features and advantages of the invention will be evident
from the following detailed description of the preferred embodiments
described in conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in conjunction with the following drawings
in which like features are designated with like reference characters, and
wherein:
FIG. 1 is a diagram showing the system of a hybrid drive apparatus for a
vehicle according to a first embodiment of the invention;
FIG. 2 is a drive mode map in a control unit of the hybrid drive apparatus
for a vehicle;
FIG. 3 is a timing chart for a process for starting the engine executed by
the control unit;
FIG. 4 is a main flow chart of the process for starting the engine;
FIG. 5 is a flow chart of a sub-routine in the main flow chart for the
standby control;
FIG. 6 is a flow chart of a sub-routine in the main flow chart for
controlling the start of the engine;
FIG. 7 is a timing chart showing a modification of the starting control
according to the first embodiment;
FIG. 8 is a timing chart for a process for starting the engine by the
hybrid drive apparatus for a vehicle according to the second embodiment;
FIG. 9 is a flow chart of a part of the sub-routine for engine starting
control to start the engine;
FIG. 10 is a flow chart showing the other part of the sub-routine for the
engine starting control;
FIG. 11 is a timing chart showing a modification of the starting control
according to a second embodiment of the invention;
FIG. 12 is a characteristic graph showing torque variance with respect to
revolutions of a crank of a generally-employed six-cylinder engine;
FIG. 13 is a graph showing a cranking torque characteristic of the
generally-employed engine;
FIG. 14 is a graph showing a start-up characteristic of the above-described
cranking torque;
FIG. 15 is a diagram showing the system of a hybrid drive apparatus for a
vehicle according to a third embodiment of the invention;
FIG. 16 is a diagram showing the system of a hybrid drive apparatus for a
vehicle according to a fourth embodiment of the invention; and
FIG. 17 is a diagram showing a hybrid drive apparatus for a vehicle
according to a fifth embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Embodiments of the invention will now be described with reference to the
drawings. FIG. 1 is a diagram showing the structure of the system of a
hybrid drive apparatus for a vehicle according to a first embodiment of
the invention. The hybrid drive apparatus for a vehicle according to the
first embodiment incorporates an engine (E/G) 1, a motor generator (M/G)
2, a clutch 3 which is capable of controlling power transmission between
the engine 1 and the motor generator 2, a transmission unit 4 which is
capable of transmitting power of the engine 1 and the motor generator 2 to
the vehicle wheels and an electronic control unit (ECU) 5 for controlling
the engine 1, the motor generator 2, a starter motor (S/M) 11 and the
clutch 3.
The engine 1 incorporates an auxiliary machine as the starter motor 11
arranged to be operated by a 12 V low-voltage battery for auxiliary units.
Like a generally-employed starter, an output gear 11a is revolved and
engaged with a wheel gear 12 secured to a crank shaft of the engine 1
during revolution of the starter motor 11. When the revolution of the
starter motor 11 has been interrupted, the output gear 11a is disengaged
from the wheel gear 12.
The motor generator 2 has a rotor 21 connected to the engine 1 through the
clutch (hereinafter called a "Ci clutch" so as to be distinguished from
other clutches) 3. Moreover, the motor generator 2 is connected to an
automatic transmission unit (T/M) 40, mainly constituting the transmission
unit 4, through an input clutch (hereinafter called a "C1 clutch") 41.
The automatic transmission unit 40, constituting the transmission unit 4,
incorporates a predetermined gear train controlled by a hydraulic control
unit (V/B) 6. An output shaft of the automatic transmission unit 40 is
connected to right and left driving wheels 8 through a differential unit
7. In the apparatus according to this embodiment, the hydraulic control
unit 6 also serves as a control unit for controlling the hydraulic servo
of the Ci clutch 3.
The control unit 5 constitutes an electronic control unit including a
microcomputer for controlling the motor generator 2 through an inverter
(not shown), the hydraulic control unit 6 through a solenoid (not shown)
and the starter motor 11 through a relay. The control unit 5 is able to
receive a signal indicating the degree of accelerator opening, a vehicle
speed signal, a signal indicating the number of revolutions input to the
transmission and a signal indicating the number of revolutions of the
engine 1 from corresponding sensors (not shown).
The control unit 5 incorporates a starting control means. The starting
control means detects the degree of accelerator opening so as to restart
the engine 1 during running of the vehicle in a state where the engine 1
is stopped and the Ci clutch 3 is disengaged to transmit the power of the
motor generator 2 to the driving wheels 8. The control unit 5 incorporates
a standby control means for revolving the engine 1 to a position at which
cranking is started prior to the process by the starting control means.
Specifically, the starting control means incorporates the standby-pressure
control means for controlling the engagement pressure of the Ci clutch 3
so as to adjust the power transmission.
Moreover, the control unit 5 has a drive mode map stored in the memory of
the microcomputer thereof. FIG. 2 graphically shows the map data. In
accordance with the relationship between the vehicle speed and the degree
of accelerator opening, the following regions are provided; an engine
drive region formed in a high negative speed (reverse drive) area when the
accelerator has been turned on; engine and motor drive regions formed in a
low positive speed area and a low negative speed (forward/reverse) area on
the two sides of a position including the vehicle speed of zero; an engine
drive region formed in a high positive speed (forward drive) area except
for an area of a low degree of accelerator opening area; a motor drive
region formed in the low degree of accelerator opening area; and a
regenerative region formed in a positive vehicle speed region (forward
movement to drive the wheel) when the accelerator is turned off. A Ci
clutch standby control region to be described later, is formed in the
motor drive region adjacent to the engine drive region.
A process for determining whether the engine 1 is stopped is made when the
control unit 5 determines that the engine 1 may be stopped in accordance
with the drive mode map shown in FIG. 2 in a case where the degree of
accelerator opening is in the motor drive region for a time not shorter
than a predetermined time. When the control unit 5 determines that start
of the engine 1 is required in a case where the degree of accelerator
opening is, conversely to the above-mentioned determination to stop the
engine 1, in the engine drive region for a time not shorter than a
predetermined time, it is determined that the engine 1 has been restarted.
When it is determined that the engine 1 should be restarted, standby
control of the Ci clutch 3 and starting control of the engine 1 are
performed. Then, it is determined that combustion has been completed and
completion control is performed. The starting control of the engine 1 is
composed of control of the start of the revolutions of the engine which is
performed in the former half portion of a cranking process, control of
acceleration which is performed in the latter half portion of the cranking
process, fuel supply and ignition. The standby control of the Ci clutch 3
can be performed at the following three moments in time. A first moment in
time is a moment when the determination to restart has been made. A second
moment in time is a moment when the Ci clutch standby control region in
the drive mode map shown in FIG. 2 has been started. A third moment in
time is a moment in time included in a predetermined period of time after
the engine stop control has been completed. A method using the
above-mentioned second timing is the most effective method. In this
embodiment, the above-mentioned methods are used inclusively.
Referring to the timing chart shown in FIG. 3 and also referring to FIG. 1,
the contents of the control will sequentially be described. At first, the
engine revolution (Ne) assumes a value of zero indicating the stop state,
the motor revolution (Nm) is gradually increased as the vehicle speed
increases, the engine torque (Te) assumes a value of zero indicating the
stop state, the motor torque (Tm) is gradually increased in an accelerated
state with the torque output in accordance with an output control map
determined previously in accordance with the degree of accelerator
opening, the Ci clutch pressure (Pci) assumes a value of zero indicating
the disengaged state and the output-shaft torque (Tout) is in a state
where it is gradually increased to correspond to the driving force
realized by the motor torque.
When the degree of accelerator opening in the motor drive region is
increased to enter into the Ci clutch standby control region, a solenoid
signal is transmitted (as indicated with a dashed line shown in FIG. 1)
from the control unit 5 to the hydraulic control unit 6. Thus, control is
performed such that the Ci clutch pressure (Pci) is, as fast-fill pressure
(Pf), supplied to the hydraulic servo of the Ci clutch 3 for a fast-fill
period of time (tf) (as indicated by a chain line shown in FIG. 1). The
fast-fill pressure (Pf) and the fast-fill period of time (tf) are
determined to be a value by which the clutch piston can quickly be stroked
and the cylinder of the hydraulic servo of the Ci clutch 3 can be filled
with oil.
Then, a similar procedure is employed such that the standby pressure
(Pstby) is applied for a standby period of time (tstby). The standby
pressure (Pstby) represents a pressure level (for example, about 100 kPa
to about 200 kPa) at which the Ci clutch 3 is able to transmit small
torque so as to slightly revolve the crank shaft of the engine 1 and at
which the crank shaft is stopped at an angular position corresponding to
the compressive torque immediately before the position corresponding to
the required compressive torque. The standby period of time (tstby) must
be, for example, about several hundreds of msec. when employing the first
or the third determination methods. If the first determination method is
employed, sweep-up control is immediately started. If the third
determination method is employed, the Ci clutch 3 is turned off. Then, a
motor drive mode is started. If the second determination method is
employed, the standby period of time (tstby) is continued until the next
control (sweep-up control) of the pressure of the Ci clutch 3 is
performed.
When the Ci clutch standby control has been performed as described above,
the torque of the motor generator 2 is transmitted to the engine 1 through
the Ci clutch 3. Thus, the engine 1 is revolved. Since the required torque
is increased at the start of compression stroke of the first cylinder, the
Ci clutch 3 is slipped. Thus, the engine 1 is stopped at the position
corresponding to the present crank angle so that the engine 1 is brought
to the standby state prior to the cranking operation. The rotational angle
for the engine 1 is not larger than about 100.degree. in a case of a
six-cylinder engine. In the above-mentioned period of time, a portion of
the motor torque (Tm) is used to revolve the engine 1 to the cranking
start position. Since low revolution resistance is, however, generated, a
great influence is not exerted to the output-shaft torque (Tout). Since
the crank angle position is always brought to be positioned before the
position at which the cranking torque is generated as described above, the
same rise characteristic of the cranking torque can be realized when the
control is started. As a result, the sweep-up response of the Ci clutch
pressure during the engine starting control can be improved.
After the lapse of the standby period of time (tstby) in which the standby
state is realized, engine start is performed by the starting control
means. In this case, the motor torque (Tm) and the Ci clutch pressure
(Pci) are increased and the starter motor 11 is started simultaneously. As
a result, the motor torque (Tm) is increased such that the increased
torque (Tcrunk) and the starting torque are added to the previous torque
(Tacc) required to drive the vehicle and corresponding to the degree of
accelerator opening. The torque is transmitted through the clutch, the
torque transmission capacity of which has been increased in conjunction
with the rise in the Ci clutch pressure (Pci), thus cranking the engine 1.
As a result, the engine 1 starts revolving while exceeding the peak torque
realized by inertia torque generated at the rise of the revolutions of the
engine 1. Although the rise of the revolutions can be determined by
detecting the engine revolution (Ne), it is determined whether off-time
(toff) of the starter motor has elapsed because the small number of
revolutions cannot accurately be detected. If the off-time (toff) has
elapsed, the starter is turned off. The state where the motor torque is
increased is maintained. When the number of revolutions of the engine 1
has been increased to a predetermined number of revolutions in this case,
ignition timing is adjusted. Simultaneously with the ignition, the motor
torque (Tm) is returned to the torque value required to drive the vehicle.
The determination with respect to completion of combustion for confirming
the start of the engine (in a state where the engine is allowed to revolve
continuously) can be performed by the method described below. A first
method uses the output of an O.sub.2 sensor provided in the exhausting
portion so as to be used to perform general control of the air-fuel ratio.
With this method, the concentration of oxygen in the exhaust gas is
reduced considerably if the combustion stroke in the cylinder is
controlled to be continuously performed. Therefore it can be determined
that the combustion has been completed. A second method used is to detect
the temperature of the exhaust gas or the temperature of a catalytic
converter for processing the exhaust gas. A third method used is to detect
the combustion pressure in the cylinder. The first method is the most
effective from among the above-mentioned methods. If an O.sub.2 sensor
provided with a heater is employed so as to stabilize the performance (the
sensitivity) of the sensor even if the temperature of the exhaust gas is
low, an even better result can be obtained. Since the third method employs
a sensor provided only for a lean-burn engine, the sensor is operated only
for determining completion of the combustion. Therefore, the third method
is disadvantageous in terms of cost reduction.
When completion of the combustion of the engine 1 has been determined, an
electromagnetic control throttle valve is opened to a degree corresponding
to the accelerator opening on the respective occasions. Thus, the number
of revolutions of the engine 1 is approximated to the input number of
revolutions to the transmission operated by the motor with the output
torque corresponding to the degree of opening of the accelerator. When the
engagement of the Ci clutch 3 has been completed (when the number of
revolutions of the engine 1 and the input number of revolutions to the
transmission are identical), the motor output torque (Tm) is swept down at
a predetermined gradient corresponding to the degree of accelerator
opening.
A specific procedure for performing the above-mentioned control will now be
described with reference to a flow chart. FIG. 4 shows a main flow for
controlling the start of the engine during the running of the vehicle. The
degree of accelerator opening is read in step S1 and the vehicle speed is
read in step S2. Thus, in step S3, it is determined whether the present
state of driving is in the engine drive region based on the drive map (see
FIG. 2). In step S4, it is determined whether the present state of driving
is in the Ci clutch 3 standby region based on the drive map. If the
determination in either of step S3 or step S4 is (Yes), the Ci clutch
standby control is executed in step S5. In step S6, the engine starting
control is executed.
FIG. 5 shows a sub-routine for the Ci clutch standby control which is
executed in step S5 as shown in FIG. 4. In the foregoing routine, the Ci
clutch pressure (Pci) is set to an initial value (Pf) for outputting in
step S21. Thus, a process for shortening the piston stroke of the clutch
is performed. The operation of the Ci clutch operated by the
above-mentioned process can be confirmed if the time (tf) has elapsed from
output of the hydraulic pressure in accordance with a timer in step S22.
After the foregoing time has elapsed, the Ci clutch pressure (Pci) is set
to the predetermined standby pressure (Pstby) to bring the engine to the
cranking start position in step S23. Then, the standby pressure (Pstby) is
output. As a result, the crank shaft of the engine is slightly revolved so
that the engine is brought to the cranking start position (prior to the
compression stroke). The cranking start position is confirmed in step S24
by determining whether the predetermined standby period of time (tstby)
has elapsed from the output of the standby pressure (Pstby). In step S25,
it is determined whether the engine drive region has been started. If the
above-mentioned determination is (Yes), the engine starting control
sub-routine is started. If the determination of the engine drive region is
(No) in step S25, it is determined in step S26 whether the state is in the
Ci clutch standby region. If the foregoing determination is (Yes), the
operation is returned to step S23 so that the Ci clutch pressure (Pci) is
maintained at the standby pressure (Pstby). If the determination of the Ci
clutch standby region is (No) in step S26, it is determined that the state
has been returned to the motor drive region. Thus, the above-mentioned
control is interrupted by executing a process for setting the Ci clutch
pressure (Pci) to zero in step S27.
The start of the engine is controlled by two methods after the
above-mentioned standby state has been realized. As a first embodiment,
control using the starter motor will now be described.
In the first embodiment, steps S31 to S33 are simultaneously executed at
the start of the engine starting control sub-routine as shown in FIG. 6.
To describe the chart for easy comprehension, the steps are expressed
sequentially. In step S31, the starter motor is started. In step S32, the
Ci clutch pressure (Pci) is set to establish Pci=(Tcrunk/m-c)/a where
Tcrunk is an average value of cranking, i.e., required starting, torque of
the engine, which has been previously determined for the engine; m is a
coefficient of friction of a friction member of the clutch; and a and c
are constants determined based on the clutch.
In step S33, an output of the motor torque (Tm) is produced. The motor
torque is set to establish Tm=Tcrunk+Tacc, where Tcrunk is the torque
required to start the engine and Tacc is the torque corresponding to the
degree of accelerator opening and required to drive the vehicle. After the
foregoing steps have been executed as described above, in step S34, it is
determined whether off-time (toff) has elapsed from the start of the
control. The foregoing time is a very short period, allowing the engine to
revolve (one revolution) slightly. If an elapse of the off-time (toff) is
confirmed, the starter motor is turned off (OFF) in step S35. Since the
starter is operated for a very short time (toff) in the above-mentioned
case, no problem arises in terms of durability of the starter and noise
generated from the start of the starter. Steps S31 to S35 described above
constitute the control of the start-up of the engine revolution.
In step S36, it is determined whether the revolution of the engine has
reached a predetermined number of revolutions (for example, 500 rpm, that
is, the number of revolutions at which the complete combustion state is
reached where the engine is able to revolve by the supply of fuel and
ignition). If the determination in step S36 is (Yes), the fuel is injected
to the engine in step S37 so that ignition is performed and, thus, the
engine is started. The above steps S32 to S36 constitute the control of
the acceleration of the engine revolution.
After the engine has been started, the motor torque (Tm) is returned to the
torque (Tacc) corresponding to the degree of accelerator opening in step
S38. The foregoing process is performed because the cranking torque
(Tcrunk) is not required after starting the engine. In step S39, it is
determined whether the engine revolution (Ne) has been synchronized with
the input number of revolutions (Nin) of the transmission within a range
of .+-.Na. If the synchronization is determined (Yes), the Ci clutch
pressure (Pci) is, in step S40, set to 100% pressure, that is, P100. Thus,
the Ci clutch is engaged completely and the torque of the engine can be
transmitted to the wheels. Therefore, a process for reducing the motor
torque (Tm) is executed in step S41. Simultaneously, an output of the
torque (Te=Tacc-Tm) decreases owing to sweep-down of the motor torque
(Tm). Specifically, a signal is transmitted to the electronic throttle so
as to open the throttle. Finally, in step S43, it is determined whether
the motor torque (Tm) has been set to zero. If the foregoing determination
is Yes, switching from the motor drive to the engine drive is completed.
The aforementioned steps S38 to S43 constitute the part of completing the
control.
The first embodiment eliminates a need for the motor generator to evaluate
the performance for outputting the cranking torque in addition to the
performance for driving the vehicle. Therefore, the size of the motor
generator can be reduced. Since the general mass-produced starter motor
for revolving the engine may commonly be employed, enlargement of the cost
can be minimized. Furthermore, if the state of charge (SOC) of a
high-voltage system (a power source for operating the motor generator) has
been set to 0% owing to self-discharge, or the like, caused from an unused
state for an extended period, an advantage can be realized in that the
engine can be started by the 12 V battery for the auxiliary units as the
generally-employed engine drive vehicle. Also, a jump start using a
booster cable can be performed. Moreover, start of the engine at very low
temperatures (-30.degree. C. to -40.degree. C.) can be performed with the
response similar to a generally-employed vehicle irrespective of the
performance of the electric oil pump at low temperatures.
The first embodiment is structured such that the motor generator 2 is
mainly operated and the starter motor 11 is supplementarily operated.
Another structure, conversely, may be employed in which the starter motor
11 is operated mainly and the motor generator 2 is operated
supplementarily. In this case, a current sensor for measuring a current
value which rushes into the starter motor is provided for the circuit for
operating the starter motor. An output value from the current sensor is
used to perform feedback control of the output torque from the motor
generator when the starting control is performed. FIG. 7 shows a timing
chart of the aforementioned control. In the control, the output torque
from the motor generator is adjusted such that the current (1st) for
operating the starter motor does not exceed a predetermined value. The
clutch pressure (Pci) is required to be simply controlled such that the
pressure is swept up to line pressure (PL) simultaneously with the start
of the starter motor after which it is kept constant. The operation of the
starter motor is interrupted when the engine revolution has increased to a
predetermined number of revolutions.
When the above-mentioned control is performed, the operation load of the
starter motor 11 can be decreased to a value equal to or smaller than a
predetermined threshold value as indicated by a solid line shown in FIG.
7. The cranking load corresponding to the peak indicated by a dashed line
shown in FIG. 7 is provided by the motor generator 2.
The first embodiment has the structure in which cranking of the engine 1 is
mainly performed by the motor generator 2. Moreover the starter motor 11
is supplementarily operated when the revolution of the engine 1 is
started. However, cranking of the engine 1 including start-up thereof can
be performed only by the motor generator 2 without operating the starter
motor 11. A second embodiment having the aforementioned structure will now
be described referring to a timing chart shown in FIG. 8.
Also in the second embodiment, the process from the initial state to the
standby control is performed in a manner similar to that of the first
embodiment. Therefore, where the process is the same, it is omitted from
the description. After the lapse of the standby period of time (tstby) in
which the standby state is realized, the starting control means starts the
engine. Unlike the first embodiment, the increase in the motor torque (Tm)
to a maximum value (Tmmax) and raising of the Ci clutch pressure (Pci) are
performed simultaneously. As a result, the motor torque (Tm) is obtained
by adding the increased torque to the previous torque (Tacc) corresponding
to the degree of accelerator opening required to drive the vehicle. Since
the torque is transmitted through the Ci clutch 3, the torque transmission
capacity of which has been increased owing to the rise in the Ci clutch
pressure (Pci), cranking of the engine 1 is performed. As a result, the
engine 1 starts revolving while exceeding peak torque realized by the
inertia torque generated at the rise time of the revolution of the engine
1. The start of the revolution (slight revolution) is determined by a
timer or the engine revolution (Ne). Then, the motor torque (Tm) is
decreased to the torque (Tmt) which is capable of increasing the number of
revolutions of the engine at a predetermined rate of change, while
maintaining the state of increase. Also in this case, the ignition timing
is determined when the number of revolutions of the engine 1 has been
increased to a predetermined number of revolutions. Simultaneously with
the ignition, the motor torque (Tm) is returned to the torque (Tacc)
required to drive the vehicle. Subsequent control is executed in a similar
manner to that of the first embodiment.
When starting the engine only by the motor generator 2, change (decrease)
in the torque (Tout) for driving the vehicle upon start of the engine
corresponds to the capacity of the torque which can be transmitted by the
Ci clutch 3. Therefore, the capacity of the torque which can be
transmitted by the Ci clutch 3 is controlled with the engagement pressure.
In consideration of the combination of the reduction in the drive torque
and the time for which the reduction is continued, a shock is reduced by
an allowable level felt by the body of the passenger on-board within a
range of the torque output performance of the motor generator 2. Thus,
generation of uncomfortable deceleration feeling can be prevented.
As an initial (a starting control) region (Ne=0 to Ne1, a predetermined
small number of revolutions) for controlling the start of the engine
requires the largest start torque in this case, the output of the torque
from the motor is set to the maximum value (Tmmax) for the aforementioned
period of time. The foregoing value varies depending on various conditions
including the vehicle speed, temperature of the battery, SOC and the like.
Simultaneously with the torque control, an output of the Ci clutch
pressure (Pci) is produced in the manner as described below. It is assumed
that the torque used to start the engine (to start revolutions) is Tmes:
Tmes=Tci (capacity of torque transmitted by the Ci clutch)=(aPci+c)m
where a and c are constants determined by the specifications of the clutch,
m is a coefficient of friction of the friction member of the clutch and
PCi is an engagement pressure of the Ci clutch. Note that m is calculated
in accordance with the slipping speed of the friction member, the pressure
applied to the pressing surface and the oil temperature as is known by
those skilled in the art.
The ratio of the torque (Tmes) to start the engine with respect to the
torque (Tmk) to drive the vehicle is determined in accordance with a
result of an evaluation of feeling on an actual vehicle. If the torque
(Tmes) to start the engine is decreased in a range of the maximum torque
(Tmmax), an output of which can be produced, time for the initial control
of the start of the engine (the starting control) region (Ne=0 to Ne1) is
elongated. In this case, the engine start response deteriorates.
Conversely if the torque (Tmes) is increased, insufficient driving torque
causes the passenger on board to feel a great shock at starting. The
aforementioned control is continued until the number of revolutions of the
engine reaches a predetermined small number of revolutions (Ne1).
In a region where the number of revolutions is small until it reaches the
small number of revolutions (Ne1), a low-cost sensor, such as an
electromagnetic pickup sensor, cannot accurately detect the engine
revolutions (Ne). Therefore, the foregoing control may be performed in
accordance with an output from a sensor for detecting the intake air
amount of the engine in place of the engine revolution (Ne).
After the aforementioned control has been performed, the constant
acceleration control is performed. The foregoing control is performed such
that the engagement pressure of the Ci clutch is feedback-controlled so
that the number of revolutions of the engine is increased at a
predetermined acceleration. When the engine revolution (Ne) has been
increased to the number of slight revolutions (Ne1), the output from the
motor is decreased to the torque (Tmt) for constantly accelerating the
engine. The foregoing torque can be determined in accordance with the
engine oil temperature (Teoil) and the engine revolution (Ne). The
aforementioned relationship can be obtained as the value of the
experimental result. In the aforementioned condition of the output from
the motor, the output of the Ci clutch engagement pressure (Pic) is
feedback-controlled such that the increase rate (dNe/dt) is set to a
predetermined value.
After the engine revolution (Ne) has reached the synchronizing number of
revolutions (Nin, an appropriate value ranging from about 500 rpm to about
700 rpm), the control of the engine for injecting fuel and ignition is
started in the similar manner to the foregoing method. Then, the
completion control is finally started. In the aforementioned control, the
driving source is switched from the motor drive to the engine drive. At
this time, a timer is set to an appropriate time after confirming the
synchronization. In order to perform reliable synchronization, the
continuously synchronized state is maintained, and then the engagement
pressure of the Ci clutch is raised to the pressure corresponding to a
duty ratio of 100%.
A sub-routine for controlling the start of the engine according to the
second embodiment is performed in accordance with a flow chart shown in
FIGS. 9 and 10. In step S51, the motor torque (Tm) is set to the maximum
torque (Tmmax), the output of which can be performed by the motor
generator in the present condition. The maximum torque (Tmmax) is the
torque with which output of both of the torque (Tmes) for starting the
engine and the torque (Tmk) for driving the vehicle can be produced. The
maximum torque (Tmmax) may be changed in accordance with the vehicle
speed, the SOC of the battery or the temperature of the battery.
Simultaneously, in step S52, the Ci clutch pressure (Pci) is determined to
establish Pci=((Tmes/m)-c)/a. That is, the Ci clutch pressure (Pci) is
determined to be a value that allows the Ci clutch pressure (Pci) to be
transmitted by the starting torque (Tmes).
In step S53, it is determined whether the engine revolution (Ne) is larger
than the predetermined small number of revolutions (Ne1). The foregoing
determination may be performed in accordance with the time measured by the
timer in place of the number of revolutions. In step S54, the motor torque
(Tm) is decreased to the torque (Tmt) with which the number of revolutions
of the engine can be increased at a predetermined rate of change. In step
S55, the Ci clutch pressure (Pci) is set to a feedback initial value (Pa).
In step S56, the present rate of change (dX2) in the number of revolutions
of the engine is obtained. In step S57, a deviation (dX) from a required
rate of change (dX1) is obtained. In step S58, changing pressure (dPci) is
obtained in accordance with the obtained deviation (dX). The foregoing
value is determined such that when the deviation (dX) is large in the
direction of the positive values, the Ci clutch pressure (Pci) is
decreased. When the deviation (dX) is large in the direction of the
negative values, the Ci clutch pressure (Pci) is increased. Thus, the
actual feedback control is executed in step S59.
In step S60, it is determined whether the engine revolutions (Ne) has
exceeded a predetermined number of revolutions (for example, 500 rpm). The
process returns to step S56 for executing the feedback control until the
foregoing determination is made. If it is determined in step S60 that the
number of revolutions of the engine has reached the predetermined number
of revolutions, the process proceeds to step S61. In step S61, it is
determined whether the state is in a combustion completed state where
ignition has occurred for the engine. The aforementioned determination can
be executed in accordance with an output from the O.sub.2 (oxygen) sensor
provided for the exhaust portion of the engine to control the air-fuel
ratio as described above. When the combustion in the cylinder is
sequentially performed in all cylinders and thus the concentration of
oxygen in the exhaust gas is considerably lowered, the aforementioned
determination can be executed. Since the aforementioned determination is
(No) in a first loop, the program proceeds to step S62 where fuel is
injected for ignition into the engine.
The following processes in steps S63 to S67 are substantially identical to
those in steps S39 to S43 according to the first embodiment. Therefore,
the similar processes are not again described.
According to the second embodiment, the engine can be restarted with a
substantially quick response under the simple control without using the
starter motor 11. Therefore, the aforementioned control is able to realize
an advantage in that the foregoing control can be applied to a hybrid
drive apparatus that has no starter motor 11.
The starting control according to the second embodiment may be modified
such that the number of revolutions of the motor traces estimated values.
In this case, the control of the output torque from the motor in the
starting control is executed in a similar manner to that of the second
embodiment. The control of the Ci clutch pressure (Pci) is performed in
accordance with a timing chart as shown in FIG. 11. That is, transition of
the motor revolution (Nm) from cranking is estimated in accordance with a
rate of change in the motor revolution (Nm) prior to the start of cranking
by a predetermined time period. Then, a deviation (e) between a required
value determined in accordance with the estimated value and the actual
motor revolution (Nm) is obtained. In order to cause the motor revolution
(Nm) to trace the required values, the output of the Ci clutch pressure
(Pci) is feedback-controlled. Preferably, the aforementioned control is
performed on the basis of an output (detected speed) from a sensor (a
resolver) for detecting the position of a magnetic pole of a motor. The
following control is executed in the similar manner to that of the second
embodiment.
Although a method may be employed such that the required value of the motor
revolution (Nm) is calculated in accordance with the vehicle speed,
satisfactory accuracy cannot be obtained because the deviation e according
to this modification is very small. If the magnetic-pole sensor of the
motor generator is employed, a satisfactory accuracy (about angular degree
ranging from tens of seconds to several minutes) can be obtained to also
detect the twisting amount of the driving system.
The description has been made such that the control system according to the
invention is applied to the driving apparatus having the specific system
structure as shown in FIG. 1. A modification of the system structure of
the transmission unit 4 will now be described. A third embodiment shown in
FIG. 15 has a structure in which a second motor generator (M/G) 2A is
disposed between the automatic transmission unit 40 and the Cl-clutch 41
in the transmission unit 4. In this embodiment, an auxiliary unit 9 is
operated even if the engine is stopped during running by employing a
structure in which the auxiliary unit 9 is connected to the motor
generator 2A with a V-belt so as to be operated synchronously. Also the
driving apparatus having the aforementioned structure is able to perform
the standby control and the starting control by methods similar to those
of the aforementioned embodiments. In the foregoing case, upon control of
the engine start, the second motor generator 2A is controlled to
compensate for the decrease in the torque. Thus, the shock owing to
starting the engine can be prevented from being exerted to the passenger
on-board. Since the other structures are similar to those of the first
embodiment, the same reference numerals are given to corresponding
elements. Therefore the corresponding elements are not described.
A fourth embodiment shown in FIG. 16 has a structure in which a planetary
gear 40A having a lock-up clutch 42 for connecting the motor generator 2
to the engine (E/G) 1 and the automatic transmission unit (T/M) 40
disposed in the transmission unit 4. Thus, parallel drive and split drive
of the engine 1 and the motor generator 2 can be performed. A sun gear 43
of the planetary gear 40A is connected to the motor generator 2, while a
ring gear 45 is connectable to the engine 1. Moreover, the carrier 44
serving as an output element is connected to the automatic transmission
unit 40. Other elements constituting the structure are similar to those of
the first embodiment. Therefore, the same reference numerals are given to
the similar elements and a description of the similar elements is omitted.
In this embodiment, when the engine is started by the motor drive method,
the lock-up clutch 42 is brought to the engaged state. Moreover, the
aforementioned standby control and the starting control are performed to
execute the control of the Ci clutch 3 and that of the motor generator 2.
A fifth embodiment, shown in FIG. 17, has a structure in which a planetary
gear 40B for connecting the motor generator 2 to the engine (E/G) 1 and a
second motor generator (M/G) 2B employed in place of the automatic
transmission unit are disposed in the transmission unit 4. Contrary to the
fourth embodiment, the sun gear 43 of the planetary gear 40B is connected
to the motor generator 2, while the carrier 44 is connected to the engine
1. Moreover, the ring gear 45 serving as an output element is connected to
the second motor generator (M/G) 2B. This embodiment is structured so that
the Ci clutch 3, as an element provided for each of the foregoing
embodiments, is removed. With the aforementioned structure of the
transmission unit, the motor drive operation is performed such that the
motor generator 2B is revolved forwards to drive the vehicle. Where the
engine 1 is stopped, support of the reaction by the motor generator 2 is
relieved by racing the motor generator 2. When the standby control is
performed to start the engine, the first motor generator 2 is slightly
revolved forwards with a small output of the torque. Thus, the standby
state is realized. Then, the starting control is performed such that the
torque of the first motor generator 2 and that of the second motor
generator 2B are simultaneously increased. Also in this embodiment, the
shock owing to starting the engine can be further minimized in a manner
similar to the third embodiment.
Although the invention has been described in its five preferred forms with
a certain degree of particularity, it is understood that the present
disclosure of the preferred form of the invention can be changed in the
details of structure and in the combination and arrangement of parts.
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